In a computerized content delivery network, electronic content items are typically distributed from a content server to a user device. A content provider (e.g., an advertiser, a retailer, a business owner, etc.) may supply the content server with a variety of different content items relating to many different products or services offered by the content provider. The content server is typically responsible for selecting a particular content item to deliver to the user device (e.g., in response to a request for content from the user device). It is often difficult and challenging to predict which content item will be most effective (e.g., to induce a sale or other conversion) or most relevant for a particular user or user device.